The present invention relates to a hydrostable thermoplastic composition comprising polycarbonate and polyester, with improved fluidity and reduced molding shrinkage rate. The present invention further relates to an article comprising or consisting of such a composition.

Compositions comprising polycarbonate and polyester have excellent appearance, mechanical properties, dimensional stability, and chemical resistance, and are widely used in various fields. Particularly, a composition composed of polycarbonate and poly(butylene terephthalate), PBT, imparts excellent mechanical properties (such as impact, ductility and dimensional stability) and chemical resistance to the polycarbonate. These compositions are useful in fields such as interior and exterior parts in automobiles specifically.

However, polyesters like PBT having a relatively high amount of -COOH end groups may affect the stability of the polycarbonate in polyester-polycarbonate blends. It is believed that the -COOH end groups of the polyester may cause the polycarbonate to lose molecular weight, resulting in a change of properties of the same. This effect may be enhanced by the presence of catalysts or catalyst residues that may be applied during the manufacture of the polycarbonate.

US 9,920,198 discloses a blend of polycarbonate (PC) and poly(lactic acid) (PLA) comprising (a) branched bisphenol APC, (b) PLA, (c) a chain extender, and (d) a glycidyl methacrylate (GMA) functionalized polyolefin copolymer/terpolymer.

US 7,923,506 discloses a molding composition comprising: (a) from 20 to 49.9 wt % of a first polyester component having an intrinsic viscosity ranging from 0.5 to 1.0 and comprising: a first polybutylene terephthalate random copolymer that (1) is derived from polyethylene terephthalate copolymers and (2) has at least one residue derived from the polyethylene terephthalate component, and (b) from 20 to 49.9 wt% of a second polyester component having an intrinsic viscosity ranging from 1.1 to 1.4 and comprising: a second polybutylene terephthalate random copolymer that (1) is derived from polyethylene terephthalate component selected from the group consisting of polyethylene terephthalate and polyethylene terephthalate copolymers and (2) has at least one residue derived from the polyethylene terephthalate component, and (c) from 0.01 to 20 wt.% of a carboxy reactive component; wherein the first polyester component, the second polyester component, and optionally at least one additive, are present in a total amount of 100 wt %.

The impact properties of compositions comprising polycarbonate and polyester may be enhanced by addition of suitable impact modifiers. Such impact modifiers may be prepared by means of an emulsion polymerization process involving the use of process aids such as emulsifiers and coagulation agents. Such process aids, to the extent these would be part of the impact modifier, may also cause decomposition of the polycarbonate, i.e. promote hydrolysis.

Further to the foregoing, it is common to add quenchers to compositions comprising polycarbonate and polyester in order to prevent transesterification of the polyester and the polycarbonate. Such quenchers are typically mildly acidic. In order to maintain a certain level of hydrolytic stability of the composition this quencher needs to be selected such that it is acidic enough to quench residual catalyst in the polyester, but at the same time it does not significantly result in hydrolysis of the polycarbonate.

Thus, in demanding applications, whereby in particular the compositions may be exposed to humidity at high temperature, it is desired to provide compositions comprising polycarbonate and polyester having an improved hydrolytic stability.

Furthermore, an injection molded article or part, prepared from a PC/PBT composition, tends to contract in size once it is removed from the mold and allowed to cool. PC/PBT compositions generally suffer from high shrinkage rate and low resistance to warpage performance, because of the presence of PBT, which is a crystalline material.

Therefore, there remains a need for blended PC/PBT thermoplastic compositions that effectively address the appropriate balance of properties required in the consumer electronics and/or automotive industry such as, for example, thermoplastic compositions that can resist exposure to humidity at high temperature, while showing good processability and dimensional stability. It is an object of the present invention to provide a thermoplastic composition having good initial mechanical properties and being suitable for use in applications wherein, the composition may be exposed to humidity at high temperatures, while improving the fluidity and reduced in molding shrinkage rate of the composition.

It is a further object of the invention to provide for a thermoplastic composition comprising polycarbonate and polyester, wherein the composition has, in combination, good hydrostability, impact properties and heat stability.

These objects are met, at least in part, in accordance with the present invention, which is directed at a thermoplastic composition comprising, based on the weight of the composition

(A) from 40 to 70 wt. % of a polycarbonate composition comprising from 0 to 50 wt. % based on the weight of the polycarbonate composition of a first polycarbonate and from 100 to 50 wt. % of a second polycarbonate, the first polycarbonate having a higher molecular weight than the second polycarbonate;

(B) from 10 to 40 wt. % of a polyester composition comprising from 30 to 70 wt. % based on the weight of the polyester composition of a first polyester and from 70 to 30 wt. % of a second polyester, the first polyester having a higher intrinsic viscosity than the second polyester;

(C) from 0.1 to 10 wt. % of a hydrolytic stabilizer composition comprising at least one compound containing epoxy functional groups

(D) from 0 to 15 wt. % of impact modifier

(E) from 0 to 5 wt. % of other components wherein, the combined amounts of (A) to (E) is 100 wt. %, and wherein the composition has, or is selected to have, in combination, a notched Izod impact retention of at least 70% determined in accordance with the method set out in the description, a heat distortion temperature, determined in accordance with ISO 75A flatwise at a load of 1.8 MPa, of at least 90 °C a melt volume rate determined in accordance with ISO 1133 (250 °C, 5.0 kg) of at least 10.0 g/10min. The invention will now be described in more detail.

In the context of the present invention the term polycarbonate is to be understood as meaning an aromatic polycarbonate. Both of the terms "polycarbonate" and "aromatic polycarbonate" accordingly shall have the same meaning and may be used interchangeably. An aromatic polycarbonate, as known to the skilled person, is a polycarbonate comprising aromatic groups.

Aromatic polycarbonates are generally manufactured using two different technologies. In a first technology, known as the interfacial technology or interfacial process, phosgene is reacted with a bisphenol, typically bisphenol A (BPA) in a liquid phase. Another well- known technology is the so-called melt technology, sometimes also referred to as melt transesterification or melt polycondensation technology. In the melt technology, or melt process, a bisphenol, typically BPA, is reacted with a carbonate, typically diphenyl carbonate (DPC), in the melt phase. Aromatic polycarbonate obtained by the melt transesterification process is known to be structurally different from aromatic polycarbonate obtained by the interfacial process. In that respect, it is noted that in particular, the so called “melt polycarbonate” typically has a minimum amount of Fries branching, which is generally absent in “interfacial polycarbonate”. Apart from that, melt polycarbonate typically has a higher number of phenolic hydroxy end groups while polycarbonate obtained by the interfacial process is typically end-capped and has at most 150 ppm, preferably at most 50 ppm, more preferably at most 10 ppm of phenol hydroxyl end-groups. Typically, the amount of phenol hydroxyl end-groups is below the detection limit.

The composition of the present invention comprises, as a component (A), 40 to 70 wt. % of a polycarbonate composition comprising from 0 to 50 wt. % based on the weight of the polycarbonate composition of a first polycarbonate and from 100 to 50 wt. % of a second polycarbonate. The amount of first polycarbonate is preferably from 0 to 40 wt. %, preferably from 0 to 35 wt. %, based on the weight of the polycarbonate composition. The amount of second polycarbonate is preferably from 100 to 60 wt. %, more preferably from 100 to 65 wt. %, based on the weight of the polycarbonate composition. It is preferred that the polycarbonate composition comprises, based on the weight of the polycarbonate composition, at least 80 wt. %, preferably at least 90 wt. %, more preferably at least 95 wt. % and even more preferably at least 99 wt. % of first and second polycarbonate. Accordingly, it is preferred that the polycarbonate composition essentially consists or consists of the first and second polycarbonate. The polycarbonate composition may comprise a further polycarbonate, but preferably does not comprise a further polymer component not being a polycarbonate.

The first and second polycarbonate may have a weight average molecular weight from 25,000 to 60,000 Daltons, provided that the first polycarbonate has a higher molecular weight than the second polycarbonate. Preferably, the first polycarbonate has a weight average molecular weight from 45,000 to 65,000 Daltons, preferably 50,000 to 60,000 Daltons, as measured by gel permeation chromatography using a polystyrene standard. The second polycarbonate may have a weight average molecular weight of from 25,000 to less than 45,000 g/mol, preferably from 30,000 to 40,000 g/mol, as measured by gel permeation chromatography using a polystyrene standard. If the polycarbonate is a mixture of two or more aromatic polycarbonates then the Mw is to be determined on the basis of the mixture wherein preferably each of the aromatic polycarbonates constituting the mixture has a Mw from 20,000 to 45,000 g/mol.

It is preferred that the polycarbonate composition comprises at least two bisphenol A polycarbonates, more preferably, the polycarbonate composition consists of two bisphenol A polycarbonates. In an aspect, the polycarbonate composition comprises or consists of two interfacial polycarbonates. In another aspect, comprises or consists of two melt polycarbonates. In yet another aspect, the polycarbonate composition comprises or consists of a mixture of an interfacial polycarbonate and a melt polycarbonate.

The polycarbonate composition preferably has a melt volume rate (MVR), determined in accordance with ISO 1133 (300 °C, 1 .2 kg) of 1 to 50 cc/10min, specifically 2 to 30 cc/10 min such as 10 - 15 cc/10 min. The polycarbonate composition may also comprise of at least one polycarbonate resin regenerated from used products (so-called recycled polycarbonate resin). The used products here can be exemplified by optical recording media such as optical disks; transparent vehicle components such as automotive window glass, automotive headlamp lenses, and windshields; containers such as water bottles; eyeglass lenses; and architectural elements such as soundproofing walls, glazing, and corrugated sheet. Also usable are nonconforming products; pulverized material obtained from, e.g., sprues and runners; and pellets obtained by melting the preceding. Recycled polycarbonate resin is preferably at most 60 wt. % and more preferably at most 40 wt. % of the polycarbonate composition present in the thermoplastic composition of the present invention.

The composition of the present invention comprises, as a component (B), 10 to 40 wt. % of a polyester composition comprising from 30 to 70 wt. % based on the weight of the polyester composition of a first polyester and from 70 to 30 wt. % of a second polyester. The amount of first polycarbonate is preferably from 40 to 50 wt. %, more preferably about 50 wt. %, based on the weight of the polyester composition. The amount of second polyester is preferably from 50 to 40 wt. %, more preferably about 50 wt. %, based on the weight of the polyester composition.

In accordance with the invention, the first polyester has an intrinsic viscosity of 1.0 to about 2.0 dl/g and the second polyester has an intrinsic viscosity of 0.4 to about 0.8 dl/g, as measured in a 60:40 phenol/tetrachloroethane mixture at 23° C.

It is preferred that the polyester composition comprises or consists of at least two poly(butylene terephthalates) (PBT), more preferably, the polycarbonate composition consists of two PBTs. For example, the polyester composition may comprise a first PBT having an intrinsic viscosity of from 1.0 to 2.0 dl/g, preferably from 1.1 - 1.4 dl/g and a second PBT having an intrinsic viscosity of from 0.4 to 0.8 dl/g, preferably from 0.4 - 0.6 dl/g.

The polyester may further comprise mechanically recycled PBT or PBT obtained from renewable sources. Polyesters such as PBT are well known to a skilled person per se. The PBT that is used in the composition of the invention may for example be a polymer comprising polymeric units derived from terephthalic acid or a diester thereof such as dimethyl terephthalate, and polymeric units derived from a butanediol, such as 1 ,4- butanediol. The PBT may have a carboxylic end group content of from 10 - 80 mmol/kg, preferably from 20 - 60 mmol/kg, more preferably 20-40 mmol/kg as determined in accordance with ASTM D7409-15.

In accordance with the invention the polyester preferably does not comprise or consist of poly(lactic acid) such as in particular the material identified as "PLA" in US 9,920,198. In accordance with the invention the thermoplastic composition preferably does not comprise poly(lactic acid) such as in particular the material identified as "PLA" in US 9,920,198.

Hydrolytic Stabilizer

In accordance with the invention, the thermoplastic composition with improved hydrolytic stability of the present invention comprises from 0.1 to 10 wt. %, preferably from 0.5 to 3 wt. % of a hydrolytic stabilizer composition comprising at least one compound containing epoxy functional groups, based on the weight of the composition. It is preferred that the composition comprises at least 80 wt. %, preferably 90 wt. % to 100 wt. % of at least one compound containing epoxy functional groups, based on the weight of the hydrolytic stabilizer composition.

The said epoxy compound may have one or more epoxy functional groups. The term "polyfunctional epoxy compound" is defined to embrace a compound having at least two epoxy functional groups. A preferred difunctional epoxy compound is 3,4- epoxycyclohexyl-3,4-epoxycyclohexylcarboxylate, commercially available as ERL-4221 epoxy from Union Carbide. Examples of other preferred difunctional epoxy compounds are bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene di-epoxide, bisphenol diglycidyl ethers, diglycidyl adducts of amides, diglycidyl adducts of carboxylic acids and the like.

Other hydrolytic stabilizers comprising epoxy functional groups may be an ethylene and/or a styrene copolymer, which include repeat units derived from ethylene, and an epoxy comonomer including, for example, glycidyl acrylate, glycidyl methacrylate, glycidyl butyl acrylate, glycidyl vinyl ether, or combinations of two or more thereof. Frequently used ethylene and/or styrene copolymers can further comprise repeat units derived from an ester of unsaturated carboxylic acid including (meth)acrylate or Ci to Cs alkyl(meth)acrylate, or combinations of two or more thereof. “(Meth)acrylate”, refers to acrylate, alkyl acrylate, methacrylate, or combinations of two or more thereof. Examples of alkyl acrylates include methyl acrylate, ethyl acrylate and butyl acrylate.

The ethylene and/or styrene copolymer can also comprise, consist essentially of, or consist of, repeat units derived from ethylene and/or styrene and an epoxy comonomer including, for example, a glycidyl ester of acrylic acid or methacrylic acid, glycidyl vinyl ether, or combinations thereof, and an additional comonomer such as carbon monoxide. Such epoxy compounds are commercially available or can be made by techniques well known to those skilled in the art.

Impact modifier

The thermoplastic composition of the invention optionally comprises an impact modifier. The amount of impact modifier may be from 0 - 15 wt. % based on the weight of the composition. Preferably the impact modifier is comprised in the composition in an amount of from 2 - 12 wt. %, more preferably from 4 - 8 wt. %.

Suitable impact modifiers are typically high molecular weight elastomeric materials derived from olefins, monovinyl aromatic monomers, acrylic and methacrylic acids and their ester derivatives, as well as conjugated dienes. The polymers formed from conjugated dienes can be fully or partially hydrogenated. The elastomeric materials can be in the form of homopolymers or copolymers, including random, block, radial block, graft, and core-shell copolymers. Combinations of impact modifiers are also used.

The impact modifier preferably comprises or consists of at least one of acrylonitrile- butadiene-styrene (ABS) polymer and/or methyl-methacrylate butadiene-styrene (MBS) polymer.

Other

The thermoplastic composition disclosed herein comprise from 0 - 5 wt. % of other components, preferably selected from the group consisting of reinforcing or nonreinforcing fillers, such as for example talc, calcium carbonate, glass flakes, glass fibers and the like, antifog agents, plasticizers, flow enhancing additives, lubricants, pigments, dyes, flame retardants, nucleating agents, thermal stabilizers, UV absorbers, UV stabilizers, dispersants, surfactants, antistatic agents, slip agents, or combinations of two or more thereof. Such further components are known to the skilled person per se.

It is preferred that the other components in accordance with the present invention comprises, based on the weight of the composition, from 0.01 to 1 wt. % of a compound selected from the group consisting of Group IB metal phosphate salts and Group I IB metal phosphate salts. Preferably, the compound is selected from the group consisting of Group IB and/or Group I IB metal acid phosphates, metal acid pyrophosphates, and metal polyphosphates, more preferably the catalyst quencher is a zinc phosphate salt. This compound is used as a quencher for catalyst or catalyst residues in the polyester.

It is preferred that the other components comprises, based on the weight of the composition, from 0.01 to 1 wt. %, preferably from 0.03 to 0.5 wt. %, of a compound containing at least one of alkali metal cations or alkaline earth metal cations and a halide anion, preferably selected from one or more of the group comprising of lithium fluoride, lithium iodide, potassium bromide, potassium iodide, sodium dihydrogen phosphate, sodium acetate, sodium benzoate, sodium caproate, sodium stearate, sodium ascorbate and magnesium caproate.

Composition

The combination of specific types and amounts materials constituting the thermoplastic composition results in a property profile in terms of, in particular, hydrostability, mechanical, dimensional and thermal properties. The examples and comparative examples disclosed herein provide the skilled person with materials that fall inside and outside the scope of the invention respectively, and thereby constitute a basis for the development of further embodiments according to the invention without undue burden.

In accordance with the invention the thermoplastic composition comprises, based on the weight of the composition,

(A) from 40 to 70 wt. % of a polycarbonate composition;

(B) from 10 to 40 wt. % of a polyester composition; (C) from 0.1 to 10 wt. % of a hydrolytic stabilizer composition comprising at least one compound containing epoxy functional groups

(D) from 0 to 15 wt. % of impact modifier

(E) from 0 to 5 wt. % of other components wherein, the combined amounts of (A) to (E) is 100 wt. %.

The amount of component (A) may be from 50 to 70 wt. %.

The amount of component (B) may be from 25 to 35 wt. %.

The amount of component (C) may be from 0.5 to 3 wt. %.

The amount of component (D) may be from 2 to 12 wt. %.

The amount of component (E) may be from 0.01 to 3 wt. %.

Component A comprises from 0 to 50 wt. % based on the weight of the polycarbonate composition of a first polycarbonate and from 100 to 50 wt. % of a second polycarbonate, the first polycarbonate having a higher molecular weight than the second polycarbonate. Component B comprises from 30 to 70 wt. % based on the weight of the polyester composition of a first polyester and from 70 to 30 wt. % of a second polyester, the first polyester having a higher intrinsic viscosity than the second polyester;

For the avoidance of doubt the skilled person will understand that the total weight of the composition will be 100 wt. % and that any combination of materials which would not form 100 wt. % in total is unrealistic and not according to the invention.

In accordance with the invention, the thermoplastic composition is selected to have in combination; a notched Izod impact retention of at least 70% determined in accordance with the method set out in the description, a heat distortion temperature, determined in accordance with ISO 75A flatwise at a load of 1.8 MPa, of at least 90 °C, preferably from 90 °C to 120 °C a melt volume rate determined in accordance with ISO 1133 (250 °C, 5.0 kg) of at least 10.0 g/10min.

In a preferred aspect, the thermoplastic composition exhibits a notched Izod impact retention of at least about 5%, preferably at least about 10%, more preferably at least about 20% higher than that of an identical composition, but not containing component (D).

Preferred ranges for the amount of the components and preferred ranges for the properties of the composition may be combined without limitation, provided of course that these fall within the scope of the invention as defined herein in its broadest form. That is to say, a preferred range for one or more of the amounts and/or types of the components constituting the thermoplastic composition may be combined with a preferred range for one or more of the properties of the thermoplastic composition and all such combinations are considered as disclosed herein.

The compositions can be manufactured by various methods known in the art. For example, polycarbonate, polyester, and other components are first blended, optionally with any fillers, in a high-speed mixer or by hand mixing. The blend is then fed into the throat of a twin-screw extruder via a hopper.

Preferably, the thermoplastic composition is prepared by the method comprising the steps of: a) combining polyester composition with the hydrolytic stabilizer composition and optionally the other components, in a first melt mixing device so as to form a stabilized polyester composition, b) combining said stabilized polyester with polycarbonate composition and optionally the impact modifier in a second melt mixing device.

The product from the second melt mixing device can be fed into the extruder. The extruder was set with barrel temperatures between 150°C and 260°C. The extrudate can be immediately cooled in a water bath and pelletized. The pellets so prepared can be 0.6 cm long or less as desired. Such pellets can be used for subsequent molding, shaping, or forming.

Shaped, formed, or molded articles comprising the compositions are also provided. The compositions can be molded into articles by a variety of methods, such as injection molding, extrusion, and thermoforming. Some example of articles include automotive and vehicular body panels such as bumper covers and bumpers or a housing for electrical equipment.

Accordingly, the present invention relates to an article comprising or consisting of the thermoplastic composition or obtainable by the method disclosed herein, wherein preferably the article is an automotive interior article, or a housing for electrical equipment.

More in particular, the present invention relates to vehicular body parts or for housing of electrical equipment comprising or consisting the thermoplastic composition disclosed herein. Likewise, the present invention relates to a an article that comprises or constitutes any one or more selected from the group consisting of instrument panels, cup holders, glove boxes, dashboards, dashboard carriers, door claddings, door fixtures, armrests, pillar cladding, seat cladding, boot cladding and parts used in heating, ventilation and/or air conditioning instruments. Furthermore, the present invention relates to a vehicle or an electrical equipment comprising said vehicular body part or said housing. The present invention relates to the use of the thermoplastic composition, or obtainable by the method disclosed herein for the manufacture of an article of manufacture, preferably an automotive part, more preferably an interior automotive part.

The present invention will now be further elucidated based on the following non-limiting examples.

Test Methods

EXAMPLES

The samples were molded by injection molding on L&T ASWA 100T Injection molding machine at 260 °C, keeping the mold temperature set at 100 °C for all compositions. The components of the compositions and their source are listed in Table 1.

Table 1 : Components of the compositions and their source

COMPARATIVE EXAMPLES (CE1 - CE4) AND EXAMPLES (E1 - E6): Table 2

Table 2: Formulations and properties for the PC/PBT thermoplastic compositions

Table 2 (contd.)

The amounts in Table 2 are in weight percent based on the total weight of the composition. In all the examples, the total amount of components, equals 100 weight percent. Table 2 shows that thermoplastic compositions comprising PC/PBT and an impact modifier viz. ABS or MBS in absence of the hydrolytic stabilizer of the present invention (CE1) do not show a desired hydro-ageing property in terms of notched Izod impact retention determined in accordance with the method set out above. In presence of a hydrolytic stabilizer containing epoxy functional groups, though the hydro-ageing property is achieved, the desired balance of properties in terms of flow properties (MVR) and dimensional stability (shrinkage) is not achieved (CE2 to CE4). In addition, thermoplastic compositions comprising a PBT composition with a specific ratio of split between high intrinsic viscosity and low intrinsic viscosity PBTs fails to show the desired balance of properties in accordance with the invention when only high molecular weight polycarbonate is used in the composition (CE5 to CE7).

However, a thermoplastic composition comprising the components in accordance with the invention is shown to demonstrate desired hydro-ageing property in terms of notched Izod impact retention, along with a good balance of thermal, flow and dimensional properties in terms of HDT, MVR and shrinkage (E1 to E12). Furthermore, a combination of two different hydrolytic stabilizers, both having epoxy functional groups, also shows similar effect in accordance with the invention.